The present invention is concerned with a device designed for separating blanks in a machine which converts sheets or plate workpieces into blanks for forming packages.
The production of packages includes three successive stages. The first stage is printing a large number of motifs or images on a sheet with each motif or image corresponding to a single package. The second stage is a die-cutting of the sheet into blanks, with each blank being provided with a single printed motif. The third stage is folding and gluing each of the blanks in order to have it transformed into a flat-folded collapsed package, which can be later erected to receive the contents.
After die-cutting, all blanks contained in a sheet are still held together by small linking points, which correspond to very small non-cutting nicks which are provided in the cutting rules of the die-cutting press. This allows the die-cut sheet to be carried by means of gripper bars, which are mounted on a pair of chains, between the platens of the die-cutting press to subsequent stations for stripping of waste bits consisting of the sheet areas between various blanks, which waste areas are to be removed from the final package, as well as to a delivery station for the sheets.
Depending on the requirements, there should be a possibility in the delivery station of providing a build-up pile of sheets, with each sheet consisting of all the blanks held together by the linking points. Another possiblity is to simultaneously build up several piles of blanks which were previously separated from one another by breaking the linking points in the preceding station called a "blank separating station".
With the present state of the art, the blank separating station is equipped with an upper movable tool and a lower fixed tool. The upper movable tool consists of an assembly of punches or blocks and the lower tool is of a matrix with apertures corresponding to the size of each of the blanks. The upper movable punches will push the blanks through these apertures of the lower matrix, thereby causing the breaking of the various linking points existing between the blanks and also to remove lateral and peripheral sheet waste. Thus, the separating tools are adapted to the configuration and location of the blanks in a sheet and for each new run of sheets to be processed a new separating tool is required. As a rule, the punches are aligned with regard to the cutting lines of the press and fitted on a base plate of the upper movable tool frame of the blank separating station. Underneath and opposite each punch, an aperture or a corresponding mesh of the lower matrix consists of small bars. These small bars are arranged in an overlapping fashion with a view of having them form a grid or matrix which meshes with the approximate dimensions of the blanks to be separated.
To avoid the necessity of making new blank separating tools for every new run of sheets, it has been proposed in U.S. Pat. No. 4,175,686, whose disclosure is incorporated herewith by reference thereto and which is based on the Swiss Application which was issued as Swiss Patent No. 617,886, to fit the punches adjustably in a horizontal direction along bars which are fitted on a vertically movable frame, with every punch having the shape of a block connected to its neighboring block by devices inserted into one another. The lower matrix consists of adjustable crossbars which are shiftable so as to form a grid with meshes and apertures adjusted, as required, to the size of the blanks.